7. Asplenium ensiforme Wallich ex Hooker & Greville, Icon. Filic. 1: t. 71. 1828.
剑叶铁角蕨 jian ye tie jiao jue
Asplenium ensiforme f. bicuspe (Hayata) Ching ex S. H. Wu; A. ensiforme var. bicuspe (Hayata) Tagawa; A. ensiforme var. parvum Tardieu & Ching; A. ensiforme f. stenophyllum (Beddome) Ching ex S. H. Wu; A. ensiforme var. stenophyllum (Beddome) Ching; A. gracilipes Ching & Y. X. Lin; A. melanolepis Baker (1890), not Franchet & Savatier (1879), nor Colenso (1888); A. tonkinense C. Christensen; A. stenophyllum Beddome; Diplazium bicuspe Hayata.
Plants 30-45(-65) cm tall. Rhizome erect, short, apex scaly; scales dark brown to black, narrowly triangular, ca. 6 × 1 mm, entire. Fronds simple and clustered; stipe stramineous, 5-8(-15) cm, base with scales, becoming subglabrous above; lamina narrowly lanceolate, 20-40(-50) × 1.5-2.5(-4) cm, base decurrent on stipe, margin entire to repand, apex acuminate to caudate. Midrib stramineous, abaxially semiterete and raised, adaxially sulcate; veins obscure, 1-forked. Fronds leathery, yellowish green or brownish when dry, subglabrous. Sori linear, 1.3-2(-3) cm, starting close to midrib at an angle of 15°-25°(-30°), on acroscopic veinlets; indusia yellowish brown or brownish green and becoming dark brown when dry, linear, papery, margin composed of thin-walled hyaline cells, fimbriate to entire, opening toward midrib, persistent. Spores without perforations in outer cristate-alate perispore. Plants sexual tetraploid: 2n = 144.
On rocks and tree trunks in forests; 800-2800 m. Guangdong, Guangxi, Guizhou, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Xizang, Yunnan [Bhutan, India, Japan, Myanmar, Nepal, Sri Lanka, Thailand, Vietnam].
Plants of Asplenium ensiforme with extremely narrow fronds, occurring at higher elevations, have sometimes been recognized as a separate species, variety, or form. A specimen from Taiwan with forked frond apices was described as "A. bicuspe" (nom. nud., cited in the protologue of Diplazium bicuspe), and we have seen such aberrant forked forms also from Yunnan. Forked fronds occur in all species of pteridophytes, often randomly in particular plants, and do not merit taxonomic status.
Plants from India were reported to be tetraploid (n = 72) by Mehra and Bir (Curr. Sci. 26: 151-152. 1957) and by Bir (Curr. Sci. 29: 445-447. 1960; Curr. Sci. 31: 248-250. 1962; Caryologia 18: 107-115. 1965). This species is similar to Asplenium holosorum; for differences, see below that species.